1. Field of the Invention
The present invention relates to a forming method and forming die for a temperature sensor which is insert-formed with a resin.
2. Description of the Prior Art
A conventional sensor enclosed in a resin case is disclosed in Published Unexamined Japanese Utility Model Application No. H4-24032. In this conventional sensor, a case is formed beforehand and a resin is poured into the case to enclose a temperature sensing element.
Another conventional temperature sensor is disclosed in Published Unexamined Japanese Patent Application No. H6129915, which has been previously filed by the applicants of the present invention. This conventional temperature sensor will be explained with reference to FIG. 4 of the drawings. In FIG. 4, a temperature sensor is shown having a temperature sensing element 1, a resin case 2, and a stopper portion 3.
The temperature sensing element 1 is a thermistor, for example, and is connected to terminals 5 via parallel twin leads 4. These twin leads 4 comprise two lead wires 4a arranged in parallel with a predetermined gap therebetween. The twin leads 4 are integrated by being covered with a cover 4b, and provide a certain amount of rigidity with respect to injection molding pressure and outside force when set in a forming die. Also, the terminals 5 have connecting portions 5a for the lead wires 4a and positioning protrusions 5b for fixing the terminals 5 to the forming die.
The resin case 2 comprises nylon resin, for example. The resin case 2 is insert-formed around one end of the temperature sensing element 1, the twin leads 4 and the portions 5a and protrusions 5b of the terminals 5. The resin case 2 also forms a connector portion 2a exposing the other ends of the terminals 5 and integrally forms a stopper portion 3 in its outer wall.
The stopper portion 3 has a complicated shape, as shown in FIG. 4, and forms a flexible arm 3a and a regulating surface 3b. The regulating surface 3b regulates the amount of deformation of the flexible arm 3a. The flexible arm 3a abuts the regulating surface 3b when the rotational torque of the stopper portion 3 engaged with an installing member 7, for example, changes. The regulating surface 3b thereby limits the rotation of the stopper portion 3.
However, in the case of the above conventional techniques, it was necessary to have a process for enclosing the temperature sensing element with resin as well as a process for forming the case, and a long time was required for the resin enclosure. In this respect, the number of processes could be reduced if the temperature sensing element is insert-formed at the same time as the case is formed.
However, in order to arrange the temperature sensing element in a predetermined position in the case, it has been necessary to perform injection molding with the temperature sensing element supported by positioning pins, for example, and to perform corrective action of removing the pins after forming is completed. As a result, traces of the pins are left in the case, causing the problem of water penetrating into the interior of the case, thereby making it necessary to either limit the temperature sensor's application or to perform a process of filling in the traces.